The present invention is also related to U.S. patent Ser. No. 09/664,671 entitled xe2x80x9cLiquid-Cooled Electrical Machine Having Parallel Flowxe2x80x9d incorporated by reference herein.
The present invention relates generally to electrical machines, and more particularly to cooling of electrical machines.
Ways are continually sought to increase the electrical output of automotive alternators. With increased electrical output comes additional heat generated in the various electrical components of the alternator. In addition, friction in the bearings which support the rotor shaft of the alternator also generates heat. Because heat generated in an alternator is frequently the factor which limits the electrical output of the alternator, effective cooling of the alternator is very important.
Circulating liquid within an alternator has been recognized as one means for providing cooling. A liquid cooling design which provides effective cooling and which can support demands for ever-reducing package size of the alternator can be particularly advantageous.
In a vehicle a cooling liquid supply may be provided by the engine cooling system. Engine coolant may be routed from the engine cooling system to cool the electrical machine. One problem associated with placing a component in the cooling system is that typically the pressure drop across the system may be substantial enough to affect the performance of the cooling system. To alleviate pressure losses bypass hoses and valves have been proposed. However, the space within automotive vehicles is scarce.
Therefore it would be desirable to minimize the space requirement for a liquid cooled electrical machine.
The present invention provides an electrical machine comprising a rotor mounted on a shaft for rotation therewith and defining an axis of rotation, and a stator disposed coaxially with and in opposition to the rotor. The electrical machine further comprises a housing enclosing the stator and the rotor, the housing having a first axial end with a wall with an inner surface and an outer surface and a second axial end with a wall with an inner surface and an outer surface. The electrical machine also includes a first cooling tube having a first end and a second end and an embedded portion thereof embedded between the first inner surface and the first outer surface. The first end and the second end of the first cooling tube have a port therebetween directly fluidically coupling the first end to the second end. A second cooling tube has a first end and a second end and an embedded portion thereof embedded between said inner surface and said outer surface of the wall of the second axial end. The first end of the first cooling tube and the first end of the second cooling tube are fluidically coupled together to permit fluid flow in parallel between the first cooling tube and the second cooling tube.
Designs according to the present invention are advantageous in that they can provide effective cooling of an electrical machine while also supporting packaging-efficient electrical machine designs.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.